Russia's "Black September" of 1999

Workers cleaning up after the Sept. 9 blast on Ulitsa Guryanova. The explosion, which resulted from nearly 400 kilograms of explosives, destroyed 108 apartments in the building and damaged 15 additional buildings.

Workers carrying debris from the blast site on Ulitsa Guryanova. Ninety-four people were killed in the explosion and 249 were injured.

A woman sitting with her belongings after the blast on Ulitsa Guryanova destroyed her apartment.

A child waiting outside with her belongings, including a pet bird, after the explosion on Ulitsa Guryanova.

People standing outside after the Sept. 13 bombing of another apartment building, this time on Kashirskoye Shosse. This was the deadliest of the September bombings, with 124 casualties.

A man standing amid the debris from the Kashirskoye bombing, which flattened an eight-story building.

Workers at the blast scene in Volgodonsk on Sept. 16, when a truck bomb exploded in front of a nine-story building, killing 17 and injuring dozens.

A building near the Volgodonsk blast site. The explosion occurred near dawn and was about ten miles away from a nuclear power plant. Shortly afterwards, Vladimir Putin, who had recently been named prime minister by then-President Boris Yeltsin, called for immediate, tighter security on other vulnerable, potentially targeted sites in the country.

A woman gathering her belongings after her apartment was destroyed in the Volgodonsk bombing.

A boy who sustained head injuries as a result of the Volgodonsk bombing standing outside one of the buildings damaged in the blast.

Two boys standing outside one of the buildings damaged in the Volgodonsk blast.

A boy lying in the hospital after being injured in the Volgodonsk bombing. (Warning: The next photograph contains graphic content.)

The body of a young woman lying in a morgue after she was killed in the Volgodonsk blast.

A woman placing flowers at the Kashirskoye bomb site a few days after the explosion. Authorities removed the debris in a matter of days, and people flocked to the site to pay their respects soon after.